1. Field of the Invention
The present invention relates to a wafer ring feeding apparatus.
2. Prior Art
One example of a conventional wafer ring feeding apparatus is described in Japanese Patent Application Laid-Open (Kokai) No. S62-106642.
This feeding apparatus comprises a wafer ring cassette which stores wafer rings at a fixed pitch in a vertical direction, an elevator device which raises and lowers the wafer ring cassette, a wafer ring conveying means which conveys out wafer rings from the wafer ring cassette one at a time to a pellet pick-up device and then returns a used wafer ring to an empty storing section of the wafer ring cassette after the semiconductor pellets are picked up from the wafer ring, and a pair of guide rails which guide both side edge portions of the wafer ring conveyed by the wafer ring conveying means. Typically, a wafer sheet is attached at its outer circumferential portion to the wafer ring, and semiconductor pellets are lined up in the X and Y directions and pasted to the wafer sheet.
The distance between the guide rails in this prior art is adjustable so as to match the width of the guided surfaces on both sides of each one of the wafer rings, and each wafer ring is stored in the wafer ring cassette so that the guide surfaces of the wafer ring are positioned inside the storing section of the wafer ring cassette. However, there may be cases where wafer rings are slightly rotated inside the wafer ring cassette and that where wafer ring is slightly offset toward one side of the wafer ring cassette. When such rotated or offset wafer rings are conveyed, they may become caught on the guide rails or the positioning sections of the wafer rings may not enter positioning pins provided on the jig holder of the pellet pick-up device.